Table validation rules ok ?

[StaphAreus]

Question I am looking at some annoying Access database for a charity and got stuck on trying to make something work that they believe used to

Two Tables

Venues
pK Venue ID
Venue Name
Venue Capacity

Booking
Venue
Name
Addr1
Addr2
Addr3
Ect

They have a query call capacity check which does the following
Count Occurrences of Venues then takes this away from venue capacity

Essentially they have a standard access form of the Booking table with a drop down box and want it to only validate if seats are still free at a venue eg if the current count for venue is less than the venue capacity.

I would love to perform this validation rule on the table

Any ideas ?

 

[ScottGem]

Do a Dcount of that Venue for that Booking and subtract from capacity.